Rifle cartridges for firearms are available in a wide range of shapes and sizes for different applications. However, the variations are not infinite, and there are important constraints on cartridge dimensions. A typical rifle cartridge has a bottleneck shape with a slightly tapered nearly cylindrical body extending from a base or head to a much more tapered conical shoulder that transitions to a nearly cylindrical neck that receives a bullet. The case head typically has a groove near the head to provide a rim for a rifle extractor to engage, enabling removal of the case from a rifle chamber after firing.
Some cartridges are “belted”, in that they have a larger diameter band near the head, with a forward facing step. The main body portion has a slightly smaller diameter than the belted portion. When a belted cartridge is chambered, the belt step provides a stop that establishes the axial position of the cartridge in the chamber. In contrast, an standard non-belted cartridge limits its insertion depth by the shoulder engaging an internal shoulder in the chamber.
While cartridges may exist in any theoretical dimension, there are a number of reason why cartridges have been limited in their dimensions.
First, the characteristics of gun powder and structural limitations on rifle actions (which define the chamber) make many extreme dimensional ratios impractical or unsafe.
Second, cartridges are generally made in “families,” which each member of the family produced from a common source or “parent” cartridge case. This can be as simple as a standard case that is necked down for a smaller bullet caliber (or expanded for a larger caliber). Parent cases may be shortened as well. Nonetheless, essentially all the modification of the parent cartridge occurs at the end of the cartridge near the mouth. There is very little that can be done after a case is made to change the dimensions near the case head in any useful manner, aside from minor (but impractical in large scale production) machining operations such as to trim the rim to a smaller rebated diameter or to machine turn off a belt.
While it is easy to conceive of cartridges outside of established families (those with established case head dimensions) there is a powerful economic barrier to creating new cartridges outside of these families, due to the large tooling cost for a new cartridge. This is one reasons why belted cartridges have persisted, even though the original reason for the belt (for historic cartridges without prominent shoulders to establish depth) does not apply to many or most modern belted cartridges.
A third limitation on cartridge dimensions is the dimensions of the actions of the rifles that are to receive them. Again, rifle actions may be conceived in any length or width, but it is impractical for rifle manufacturers to generate a new size for a new cartridge that may be proposed (and there is a powerful disincentive to develop a cartridge for which there are no rifles capable of shooting it—or if the only rifles that do receive it are needlessly heavy, large or expensive.) Thus rifle actions (in the field of bolt action rifles for this discussion) are generally produced in just a few limited size categories. Even competing rifle makers use the same standard sizes, because they are producing rifles for the same market of standard ammunition.
A bolt-rifle's action will have a main elongated lower opening rearward of the chamber through which a cartridge is received (this opening may be on the side or top for single shot rifles). The opening has a length that limits the cartridge overall length (COL) that can be received, and this opening length essentially defines the length of the action. While it is disadvantageous to employ an action that is significantly longer than needed for a given cartridge due to weight, cost, size, and strength reasons, slight excess length is tolerated. Thus, there are only a limited number of action (opening) lengths produced.
A “short action” closely accepts a cartridge with a maximum COL of 2.84 inch. This is sized to optimally receive the 308 Winchester cartridge, for instance.
A “long action” closely accepts a cartridge with a maximum COL of 3.34 inch. This is sized to optimally receive the 30-06 Springfield cartridge, for instance.
A “magnum action” closely accepts a cartridge with a maximum COL of 3.60 inch. This is sized to optimally receive the 375H&H Magnum cartridge, for instance.
The width of the action opening limits the diameter of the accepted cartridge. Typical actions are provided in one of three standard widths, to provide standardization for the reasons noted above.
A standard width action admits a cartridge with a maximum diameter of 0.473 inch. This is sized to closely accommodate the 308 Winchester, and the 30-06 Springfield cartridges, for instance.
A magnum width action admits a cartridge with a maximum diameter of 0.532 inch. This is sized to closely accommodate the following example cartridges:                350 Remington Magnum (a short-action belted cartridge)        6.5 mm Remington Magnum (a short-action belted cartridge)        300 Winchester Magnum (a long-action belted cartridge)        7 mm Remington Magnum (a long-action belted cartridge)        375H&H Magnum (a magnum-length-action belted cartridge)        Lazzeroni 6.53 Scramjet (a magnum-length-action unbelted cartridge.)        
A super magnum width action admits a cartridge with a maximum diameter of 0.580 inch. This is sized to closely accommodate the 378 and 460 Weatherby (super magnum length belted cartridges), for instance. The 300 Winchester Short Magnum (WSM) also requires an action larger than a magnum-width action (whether a special width or a super magnum width action) because its 0.555 inch base diameter does not fit in a magnum-width action. The WSM has a reduced or rebated rim with such diameter to be accommodated by standard magnum bolts, with the stability and feeding disadvantages associated with rebated rims.)
The above standard sizes creates a 3-by-3 “grid” with nine bins into which the main category of centerfire bottlenecked rifle cartridges are necessarily categorized. In certain bins, the cartridges previously developed to fit the dimensional constraints have limitations on the power available to shooters.
The present invention overcomes the limitations of the prior art by providing a centerfire rifle cartridge with a case having a head having a rim, a body extending from the head to a tapered shoulder, and a neck extending from the shoulder and defining a mouth receiving a bullet. The body has a straight external surface free of a protruding belt, and has a maximum diameter sized to closely fit for operation within a standard action of magnum width. The cartridge has an overall length sized to closely fit for operation within a standard action such as a short action or a long action.